Cap for an implantable electrical lead assembly

ABSTRACT

A cap for an implantable medical device electrical connector lead assembly and methods of use. A cap for protecting an electrical connector lead assembly of an implantable medical device is disclosed. The cap includes a body defined by a mating surface and a non-mating surface. The mating surface is adapted for electrically insulating engagement with an electrical connector lead assembly of an implantable medical device. The cap includes a body having a mating surface and an electrical network disposed therein. The electrical network includes first and second contacts exposed at the mating surface, a first circuit element, and two conductive pathways connecting the contacts to the circuit element. The body is configured to mate with the electrical connector lead assembly such that each contact conductively engages a corresponding contact of the electrical connector lead assembly when the cap and electrical connector lead assembly are mated.

BACKGROUND

1. Field of the Invention

The present invention relates generally to implantable electrical leads,and more particularly, to a cap for an implantable electrical leadassembly.

2. Related Art

Devices that have one or more components designed for temporary orpermanent implantation in a recipient provide numerous therapeuticand/or other benefits. Examples of such implantable medical devicesinclude implantable medical devices such as cardiac assist devices,pacemakers, hearing prostheses, drug delivery devices, monitoringsystems, and so on. Oftentimes, implantable medical devices havemultiple implantable components. Typically, the implantable componentsare connected to each other electrical lead assemblies suitable fortransferring data, instructions, programs and other information, as wellas power, between the implanted components.

Some implantable medical devices are designed to be arranged indifferent configurations, with some configurations having a differentcombination of implantable components. The implemented configuration ofsuch implantable medical devices may change over time as the treatedcondition or desired functionality changes. Other implantable medicaldevices are designed to accept new implantable components in the future.As such, it is not uncommon for implantable medical devices to includeimplantable components which have one or more electrical lead assembliesthat are not connected to another implantable component at time ofsurgery. Such electrical lead assemblies may be associated with anunused configuration or may be provided to facilitate incorporation of anew component in the future.

SUMMARY

In accordance with aspects of the present invention, a cap forprotecting an electrical connector lead assembly of an implantablemedical device is disclosed. The cap includes a body defined by a matingsurface and a non-mating surface. The mating surface is adapted forelectrically insulating engagement with an electrical connector leadassembly of an implantable medical device.

In accordance with one aspect of the present invention a cap for animplantable medical device electrical connector lead assembly isdisclosed. The cap includes a body having a mating surface and anelectrical network disposed therein. The electrical network includesfirst and second contacts exposed at the mating surface, a first circuitelement, and two conductive pathways connecting the contacts to thecircuit element. The body is configured to mate with the electricalconnector lead assembly such that each contact conductively engages acorresponding contact of the electrical connector lead assembly when thecap and electrical connector lead assembly are mated.

In accordance with another aspect of the present invention methods ofassessing the integrity of a capped electrical connector lead assemblyof an implanted device are disclosed. The cap includes a first circuitelement connected across conductive pathways of the electrical connectorlead assembly. In such methods, a voltage is applied across theconductive pathways of the implanted electrical connector lead assembly.A characteristic, e.g., impedance, of the network across the conductivepathways is measured. The measured characteristic is compared to anexpected value of the network characteristic, e.g., the impedance of thefirst circuit element in typical cases where the impedance of theelectrical connector lead assembly is negligible.

In accordance with a further aspect of the present invention methods ofusing a magnetic location module to locate an electrical connector leadassembly of an implanted device that is terminated with a cap aredisclosed. The cap includes an electromagnetic induction coil connectedacross conductive pathways of the connector lead assembly. In suchmethods, the magnetic induction coil is energized through the conductivepathways of the connector lead assembly. A magnetic field is generatedin the magnetic location module. The magnetic location module is movedin proximity to a suspected location of the cap. The location of maximummagnetic coupling between the magnetic location module and the energizedelectromagnetic induction coil is determined.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosed technology are described below withreference to the attached drawings, in which:

FIG. 1 is a perspective view of an exemplary implantable medical device,namely an implantable medical device commonly referred to as a cochlearimplant, which in connection with embodiments of the present inventionmay be advantageously implemented;

FIG. 2 is a perspective view of an embodiment of the cochlear implantinternal component illustrated in FIG. 1, depicting the lead assemblies;

FIGS. 3A-3D illustrate four example lead assemblies, each with a cap(shown in cross section) in accordance with the present technology.

FIGS. 4A and 4B are perspective views of a four-electrode male connectorand a cap for the connector in accordance with the present technology.

FIG. 5 is a schematic view of an embodiment of the implanted componentof FIG. 2, depicting an electrical connector lead assembly of theimplanted component;

FIG. 6 is a schematic view of embodiments of a cap of the presenttechnology in relation to the implanted component and connector leadassembly of FIG. 5;

FIG. 7 is a schematic view of embodiments of a cap of the presenttechnology, containing a conductive pathway, in relation to theimplanted component and connector lead assembly of FIG. 5;

FIG. 8 is a schematic view of embodiments of a cap of the presenttechnology, containing a capacitor, in relation to the implantedcomponent and connector lead assembly of FIG. 5;

FIG. 9 is a schematic view of embodiments of a cap of the presenttechnology, containing an inductor, in relation to the implantedcomponent and connector lead assembly of FIG. 5;

FIG. 10 is a schematic view of embodiments of a cap of the presenttechnology, containing a magnetic induction coil, in relation to theimplanted component and connector lead assembly of FIG. 5;

FIG. 11 is a schematic view of embodiments of a cap of the presenttechnology, including a conductive plate, in relation to the implantedcomponent and connector lead assembly of FIG. 5;

FIG. 12 illustrates methods of assessing the integrity of a connectorlead assembly of an implanted device that is terminated with a cap inaccordance with the present technology;

FIG. 13 illustrates methods of locating a connector lead assembly of animplanted device that is terminated with a cap in accordance with thepresent technology; and

FIG. 14 illustrates methods for communicating with an implanted devicehaving a connector lead assembly with a cap in accordance withembodiments of the present technology.

FIG. 15 illustrates a radial cross section and a longitudinal crosssection of a cap in accordance with the present technology.

FIG. 16 illustrates a cap in accordance the present technology mating toa connector lead assembly of an implantable medical device.

DETAILED DESCRIPTION

Aspects of the present invention are generally directed to a cap for anelectrical lead assembly of an implantable medical device (IMD), andmethods of using the cap for lead integrity testing, for locating theconnector lead assembly, and for communicating with the IMD.

In some embodiments, the cap includes a body in which an electricalnetwork is disposed, the electrical network comprising first and secondcontacts, a first circuit element, and two conductive pathwaysconnecting the contacts to the circuit element. The body is configuredto mate with the connector lead assembly. The contacts are disposedproximate to or on a mating surface of the cap such that each contactconductively engages a corresponding contact of the connector leadassembly when the cap and connector lead assembly are mated. In someembodiments, the electrical network further comprises a second circuitelement series-connected to the first circuit element, and a conductiveplate conductively exposed to the exterior of the cap and electricallyconnected to a conductive path between the series-connected circuitelements.

Further, embodiments of the cap may be used to assess the integrity ofthe lead assembly of an implanted device. Once the lead assembly iscapped with a cap of the present invention, a voltage is applied acrossthe conductive pathways of the lead assembly. A characteristic, e.g.,impedance, of the network across the conductive pathways can bemeasured. The measured characteristic is compared to an expected valueof the network characteristic, e.g., the impedance of the cap circuitelement, since the impedance of the connector lead assembly is typicallynegligible in most arrangements

Further, embodiments of the above cap may be used to locate a connectorlead assembly. In some embodiments, the cap includes a magneticinduction coil that can be energized through the conductive pathways ofthe lead assembly. A magnetic field is generated in a magnetic locationmodule. In use, the magnetic location module is moved over the skin ofthe recipient. When it is proximate to the cap, an induction coil in thelocation module becomes magnetically coupled to the induction coil inthe cap. The location of maximum magnetic coupling between the magneticlocation module and the magnetic induction coil is determined as thelocation of the cap.

Aspects and embodiments of the present invention, while finding utilityin connection with any type of implantable electrical lead, aredescribed herein in the context of electrical lead assemblies commonlyused in cochlear implants.

FIG. 1 is a perspective view of an exemplary cochlear implant 100implanted in a recipient having an outer ear 101, a middle ear 105, andan inner ear 107. Cochlear implant 100 comprises an external component142 that may be directly or indirectly attached to the body of therecipient, and an internal or implantable component 144 that may betemporarily or permanently implanted in the recipient.

External component 142 typically comprises one or more sound inputelements, such as microphone 124 for detecting sound, a sound processingunit 126, a power source (not shown), and an external transmitter unit128. Sound processing unit 126 processes the output of microphone 124that is positioned, in FIG. 1, by auricle 110 of the recipient. Soundprocessing unit 126 generates encoded signals that are provided toexternal transmitter unit 128.

Internal component 144 comprises an internal receiver unit 136, astimulator unit 132, an elongate stimulating lead assembly 118, and aconnector lead assembly 116 for connecting to other implantablecomponents. Internal receiver unit 136 and stimulator unit 132 arehermetically sealed within a biocompatible housing, sometimescollectively referred to as a stimulator/receiver unit 120. Internalreceiver unit 136 comprises an internal coil 136 that receives power andstimulation data from external coil 130. Elongate stimulating leadassembly 118 has a proximal end connected to stimulator/receiver unit120, and extends through mastoid bone 119. Lead assembly 118 has adistal region, referred to as electrode assembly 145, implanted incochlea 140. Stimulator unit 132 generates stimulation signals that areapplied by electrode assembly 145 to cochlea 140, thereby stimulatingauditory nerve 114.

FIG. 2 is a perspective view of an embodiment of internal component 144illustrated in FIG. 1. As noted, internal component 144 comprises areceiver unit 136, a stimulator unit 132 and two lead assemblies 116 and118. Connector lead assembly 116 is configured to connect internalcomponent 144 to a separate implantable component. To this end, thesecond lead, lead assembly 116 includes an electrical connector 208Athat mates with a connector 208B of a separate module. The separatemodule can be, for example, a microphone or other sound transducer, apower source, and/or a speech processor.

In this exemplary application, use of connector lead assembly 116 isoptional. If not used in a particular recipient at the time of initialimplantation, lead assembly 116 remains dormant in the recipient untilit is used in the future. Prior to such subsequent use, connector leadassembly 116 may be damaged or may migrate to an unknown location in therecipient. Also, the lead or connector may be damaged at any time priorto or during surgical implantation. Even without migration of theconnector lead assembly, the location of the interface may not be knownat the time of the upgrade.

In some embodiments, during the period of use of the implant, an unusedconnector is terminated with a cap. FIGS. 3A-3D are cross-sectionalviews of four exemplary lead assemblies 310A-D, each having a lead314A-D and connector 316A-D, respectively. A cap 350A-D, respectively,is mated to connector 316A-D. Lead assembly 310A terminates in a paddleconnector 316A having six (6) contacts 312, while connectors 316B and316C each have two contacts 312, and connector 316D has two contacts312. Each contact 312 is electrically connected to a conductive path 318that traverses the respective lead 314. It should be appreciated thatwhile the each conductive path 318 is electrically insulated from otherconductive paths 318 in the same lead 314, in some of the illustrativeembodiments, a single conductive path 318 representing the appropriatequantity of conductive paths 318 is depicted in the figure.

Referring to cap 350A as exemplary of caps 350B-D, cap 350A includes acap body 352 defined by a mating surface 354 and a non-mating surface356. Cap body 352 can be made of a biocompatible electrically insulatingmaterial such as silicone, polyurethane, polyurethane or PTFE, and insome embodiments, is reinforced. In one embodiment, the reinforcement isin cap body 352, and in other embodiments, the reinforcement surroundsthe cap body. The reinforcement can include one or more helically woundwires, and the stiffness of the reinforcement can vary along the lengthof the cap, e.g., by varying the pitch of the helical winding. In someembodiments, the reinforcement is a tube, which can be perforated. Thestiffness of the tube can be varied by varying the size and spacing ofthe perforations. In alternative embodiments, the reinforcement is apatterned mesh, and the stiffness of the patterned mesh can vary alongthe length of the cap. Suitable materials for reinforcement includepolymers or metals such as polyurethane, titanium, platinum, iridium orgold.

Cap mating surface 354 is adapted to create an electrically insulatingseal at least at contacts 312 of connector 316. Embodiments of cap body352 also protect portions of lead 314 adjacent to connector 316. Forexample, cap bodies 352A-C each has an elongate section 354A-C thatdefine an elongate volume for receiving (not necessarily in electricallyinsulatingly sealing engagement) a portion of lead 314A-C, respectively.Depending on the anticipated environment and cap embodiment, protectionincludes any combination of protection from fluid ingress, tissuegrowth, mechanical damage (which can be done with a scalpel, a needle,or other sharp object).

FIGS. 4A-4B are perspective views of a cap 400 and a four-electrode maleconnector 410. In this illustrative embodiment, cap 400 includes removalfeatures. A first removal feature is shown as flap 420 for gripping andtearing the cap 400. A second removal feature is a weakened region,shown as a groove 430 on the outside of cap 400. Groove 430 can beplaced on the inside of cap 400. In some embodiments, a filament (notshown), e.g., a thread or a wire, can be run along the weakened region.One or both ends of the filament can be left top protrude out of thecap. Such an end can be grasped, e.g., by fingertips or an instrument,and pulled, severing the cap and either releasing or weakening it. Botha filament and a groove can be used in conjunction as removal features.

In some embodiments, the cap includes a body in which an electricalnetwork is disposed. The electrical network comprising at least firstand second contacts, at least one circuit element, and conductivepathways connecting the contacts to the circuit element. The circuitelement(s) include, for example, a conductive pathway, an electricalimpedance, and a magnetic induction coil. In some embodiments, thenetwork also includes a conductive plate for contacting the recipient'sbody. The cap body is configured to mate with the implanted deviceconnector lead assembly. The contacts are disposed on a mating surfaceof the cap such that each contact conductively engages a correspondingcontact of the connector lead assembly when the cap and connector leadassembly are mated. The present technology can facilitate connector leadassembly integrity testing (e.g., short circuit, open circuit,insulation damage), connector lead assembly location, and communicationwith the implanted device (e.g., for device diagnostics) from outsidethe recipient. These features can be provided by embodiments of thepresent technology prior or during surgical intervention, e.g., prior toimplanting an upgrade.

FIG. 5 is. a schematic view of a stimulator 514 (representing animplantable medical device) having a connector lead assembly 510.Connector lead assembly 510 includes a lead 520 and a connector 530.Lead 520 includes at least two (2) conductive pathways 522 a, 522 bseparated from each other by insulation 524, and separated from theimplantation environment by insulation 524. Connector 530 includescontacts 536 a, 536 b. Contacts 536 are formed for mating engagementwith the contacts of a mating cap, and the contacts of a matingconnector. Connector 530 includes an electrically insulating connectorbody forming a connector mating surface 539 compatible with acorresponding mating surface of each of a connector lead assembly, acap, and a load. Conductive pathways 522 a, 522 b can be connected tocircuit element 501 a, which can be an interface circuit element forconnection to, for example, upgrade modules, and can be a test circuitelement used in connector lead assembly 510 integrity testing andconnector 530 location. Suitable material for the insulating connectorbody includes biocompatible material such as silicone, PTFE orpolyurethane.

While the conductive pathways 502, and 522 are shown schematically assingle lines for ease of illustration, actual conductive pathways can beof other types and quantities as known to those of skill in the art. Forexample, conductive pathways can be co-axial, conductive pathways can bebraided, conductive pathways can be twisted, the conductive pathways canbe shielded, etc. While insulation 524 is identified by a singlereference numeral, insulation 524 can be of different type (e.g.,silicone, parylene, PTFE) and quantity between the conductive pathways,and between the conductive pathways and the implantation environment.

FIG. 6 is a schematic view of embodiments of a cap 600 of the presenttechnology in relation to the stimulator unit 514 and connector leadassembly 510 (as distinguished from the stimulating lead assembly 118 ofFIG. 1 and FIG. 2) of FIG. 5. Cap 600 includes cap body 610, at leastone circuit element 620, and cap conductors 630 a, 630 b that connectedthe cap circuit element 620 to cap contacts 640 a, 640 b. Contacts 640,640 b are formed for mating engagement with contacts of connector leadassembly 510. Cap mating surface 602 is compatible with a correspondingmating surface of a connector lead assembly. Cap circuit element 620 canbe characterized by an electrical impedance that can be resistive,capacitive, and inductive. Cap circuit element 620 can be a passiveelement such as a resistor, capacitor, inductor, and passive antenna;and can be an active element such as a transmitter, receiver, and atransceiver. In each case, cap circuit element 620 enables at least oneof testing and location of implanted devices.

In some embodiments, cap 600 includes a drug-doped component, thatincludes a host material, a drug embedded in the host material, and mayfurther include a sacrificial material integrated with the hostmaterial. The sacrificial material can facilitate the release of theembedded drug from the drug-doped component of the cap. The sacrificialmaterial can facilitate the release of the drug from the drug-dopedcomponent through the creation of voids in the host material upondissolution of the sacrificial material upon contact with a solvent. Thecontact with a solvent can be upon implant of the component in arecipient, e.g., body fluid as the solvent. The host material can be oneor more of a polysiloxane and a silicone rubber.

The drug can be one or more of an anti-inflammatory, an antimicrobial, agrowth factor, an antibody, an anti-oxidant, an antibiotic, and acorticosteroid. The cap can include a single drug or a combination oftwo or more drugs, selected from the group consisting of: anti-oxidants(e.g., nitric oxide), antibiotics, anti-inflammatories,immuno-modulators, enzymes or molecules that are known to dissolve ordegrade the components of a tissue capsule (e.g. collagenase, thrombin,fibrinolysin, trypsin, hyaluronidase, or a combination thereof),hormones or other analogs (e.g., luteinizing-hormone-releasing hormone,steroids, corticosteroids, growth factors), antibodies (e.g.,anti-vascular endothelial growth factor antibodies, tumor necrosisfactor inhibitors), cytokines (e.g., α-, -β, or γ-interferons),interleukins (e.g., IL-2, IL-10). In general, the drug can be use fortreating, decreasing the risk of, and preventing in whole or in part:infection and biofilm formation, inflammation and fibrotic tissueencapsulation, and tissue integration.

The sacrificial material can be one or more of: a glucose monomer, asugar, cyclodextrin, a material that is at least one of dissolvable andresorbable in the environment of an implant site, a salt, abioresorbable material, hyaluronic acid, polyurethane, polyester,polyamide, polyvinyl alcohol, and polyacrylic acid. In some embodiments,the sacrificial material is the host material, and the sacrificialmaterial facilitates the release of the drug from the drug-dopedcomponent through changing a property of the sacrificial material. Thechange in property can be brought about by exposing the drug-dopedcomponent to an ethanol wash. For a cap comprising a drug-dopedcomponent, the drug doped material can be applied at a distance fromconductive pathways. The drug doped material can be a physical featureof the cap, such as a region at or towards the surface. including aridge or a spine.

FIG. 7 is a schematic view of embodiments of a cap 700 of the presenttechnology, containing a conductive pathway circuit element 720 inrelation to the stimulator 514 and connector lead assembly 510 of FIG.5. Conductive pathway 720 can be used to test for open circuits incircuit 790. For example, stimulator 514 can be commanded, e.g. viasignals from external coil 130 to internal coil 136, to test theresponse of circuit 790. Any response that shows a resistance between522 a and 522 b above a threshold (with circuit element 501 a equal toan open circuit) can be interpreted as indicating an open circuit incircuit 790. Such a result can be taken as indicative of an open circuitin connector lead assembly 510.

FIG. 8 is a schematic view of embodiments of a cap 800 of the presenttechnology, containing a capacitive circuit element 820 in relation tothe stimulator 514 and connector lead assembly 510 of FIG. 5. Capacitivecircuit element 820 can be used to test for both open circuits andshorts in circuit 890.

For example, stimulator 514 can be commanded, e.g. via signals fromexternal coil 130 to internal coil 136, to test the response of circuit890 by placing a DC voltage, with minimal or no AC component, acrossconductive pathways 522 a and 522 b using circuit element 501 a. Anyresponse that shows a current flow in circuit 890 above a thresholdunder these conditions indicates a short circuit.

As a further example, stimulator 514 can be commanded, e.g. via signalsfrom external coil 130 to internal coil 136, to test the response ofcircuit 890 by placing a AC voltage, with no DC bias, across conductivepathways 522 a and 522 b. A response that deviates from thecharacteristic response of capacitive circuit element 820 can be anindication of an open circuit (no response) or a short circuit (aresponse with a DC bias).

FIG. 9 is a schematic view of embodiments of a cap 900 of the presenttechnology, containing an inductive circuit element 920 in relation tothe stimulator 514 and connector lead assembly 510 of FIG. 5. Inductivecircuit element 920 can be used to test for both open circuits andshorts in circuit 690.

For example, stimulator 514 can be commanded, e.g. via signals fromexternal coil 130 to internal coil 136, to test the response of circuit690 by placing a DC voltage, with minimal or no AC component, acrossconductive pathways 522 a and 522 b using circuit element 501 a. Aresponse that shows a resistance between 522 a and 522 b above athreshold (with circuit element 501 a equal to an open circuit) can beinterpreted as indicating an open circuit in circuit 990. Such a resultcan be taken as indicative of an open circuit in connector lead assembly510.

As a further example, stimulator 514 can be commanded, e.g. via signalsfrom external coil 130 to internal coil 136, to test the response ofcircuit 990 by placing a AC voltage, with no DC bias, across conductivepathways 522 a and 522 b using circuit element 501 a. A response thatdeviates from the characteristic response of inductive circuit element920 can be an indication of an open circuit (no response) or a shortcircuit (a response with a DC bias).

FIG. 10 is a schematic view of embodiments of a cap 1000 of the presenttechnology, containing a magnetic induction coil 1020 in relation to thestimulator 514 and connector lead assembly 510 of FIG. 5. Magneticinduction coil 1020 can be used to locate cap 1000, and by extensionlocate connector 530.

For example, stimulator 514 can be commanded, e.g. via signals fromexternal coil 130 to internal coil 136, to power circuit 1090. Locationmodule 1010 can be used to determine the location of cap 1000 throughdetermining the point of maximum magnetic coupling between locationmodule 1010 and powered magnetic induction coil 1020. In someembodiments, a permanent magnet without circuit connections to thestimulator 514 can be used for the same purpose and in the same fashionas a magnetic induction coil 1020 for locating cap 1000 (and byextension locating connector 530). In various embodiments of the presenttechnology, either of, or both of, the induction coil 1020 (implantable)or the location module 1010 can be energized; and either can be thedetected coil. For clarity, the present technology can provide aprimarily two-dimensional (2D) location of the cap, e.g., the positionon an implant recipient's skin closest to the cap. In other embodiments,the location module can provide information relating to the depth of theconnector, for example, by the magnitude of magnetic coupling.

FIG. 11 is a schematic view of embodiments of a cap 1100 of the presenttechnology, containing a conductive plate 1160 and circuit elements 1120a, 1120 b in relation to the stimulator 514 and connector lead assembly510 of FIG. 5. Conductive plate 1160 is in electrical communication witheach of circuit elements 1120 a and 1120 b via conductive pathway 1130c. A break 1170 in insulation 524, such as a scalpel cut to the lead, isshown in FIG. 10 that exposes conductive pathway 522 a to bodily fluids,thereby creating undesirable conductive pathway 1180.

Without the break 1170, circuit 1190 should provide a responsecharacterized by circuit elements 1120 a and 1120 b in series. With thebreak 1170, the electrical impedance presented by circuit element 1120 awill be in parallel with the electrical impedance presented byundesirable conductive pathway 1180 through conductive plate 1160,thereby changing the response of circuit 1190. Making the electricalimpedance of circuit element 1120 a different than the electricalimpedance of circuit element 1120 b allows an asymmetric break in theinsulation 524 to be identified. In some embodiments, a single circuitelement can be used in combination with a conductive plate or electrodeexposed to the surface of the cap.

As with the embodiments illustrated in FIG. 8 and FIG. 9, theembodiments illustrated in FIG. 11 can be used to test for open andshort circuits in a manner consistent with the electrical impedancecharacteristics of circuit elements 1120 a and 1120 b, along with beingused to determine the location of the cap 1100 where at least onecircuit element has electromagnetic characteristics that allow it to belocated by a location module 810. In addition, an electromagnetic linkbetween a location module 810 and the cap 1100 can allow datacommunication between the location module and the cap—and by extensionbetween the location module and the stimulator 514. Such a communicationchannel can find use as a backup to the communication link between theexternal coil 130 and the internal coil 136, described in connectionwith FIG. 1.

Referring to FIG. 12, methods 1200 of assessing the integrity of aconnector lead assembly of an implanted device that is terminated with acap in accordance with the present technology are shown. The capincludes an electrical impedance connected across conductive pathways ofthe connector lead assembly. In the methods a voltage is applied acrossconductive pathways of the connector lead assembly at the implanteddevice 1210. The electrical impedance across the conductive pathways ofthe connector lead assembly is determined 1220. The determinedelectrical impedance is compared to the cap electrical impedance 1230. Adifference between the determined electrical impedance and the capelectrical impedance above a threshold value is an indication that theconnector lead assembly has not maintained its integrity sinceimplantation.

More generally, where an electrical connector lead assembly of animplanted device is terminated in a cap of the present technologyincluding a circuit element as described above, the following method canbe employed to assess the integrity of the implanted electricalconnector lead assembly. A voltage can be applied across conductivepathways of the electrical connector lead assembly. A characteristic,e.g., impedance, of the network formed by the lead assembly conductivepathways and the cap can be measured. The measured characteristic can becompared to the expected characteristic of the network, e.g., for a leadassembly with negligible impedance, such characteristic is the knownimpedance of the cap circuit element. If the measured characteristic iswith an acceptable range of the expected characteristic, then theintegrity of the lead assembly has been confirmed. I f not, thendepending on the type of network in the cap, other conclusions can bedrawn, e.g., as described above in connection with FIG. 7-FIG. 12.

Referring to FIG. 13, methods 1300 of locating a connector lead assemblyof an implanted device that is terminated with a cap in accordance withthe present technology are shown. The cap includes at least one of: anatural magnet and a magnetic induction coil. In the methods, if the capincludes a magnetic induction coil, the magnetic induction coil isenergized 1310. A magnetic field is generated in at least one of: thecap and the location module 1320, then the location module is moved inproximity to a suspected location of the cap 1330. The location of thecap is determined as under the location of maximum magnetic couplingbetween the location module and the cap 1340.

Referring to FIG. 14, methods 1400 for communicating with an implanteddevice having a connector lead assembly are illustrated. In suchmethods, the connector lead assembly is capped 1410 with a cap. The capincludes a body, at least one first contact, at least one secondcontact, a communicating circuit element, and at least two conductivepathways. The cap body includes a mating surface. The cap body isengageable with the connector lead assembly at the cap mating surface.Each contact disposed on the cap mating surface such that each contactconductively engages at least one corresponding connector lead assemblycontact when the cap body is engaged with the connector lead assembly. Acircuit is formed from a first contact to a second contact, andcontaining the communicating circuit element and at least two capconductive pathways. The capped connector lead assembly can be implanted1420 in a recipient. An external communication element is coupled toimplanted device with an energy field 1430. The coupling energy field ismodulated with information in at least one direction 1440. In someembodiments of the method, the energy field is a non-propagatingmagnetic field.

In some situations, a liquid material such as silicone may be used tocoat at least the surface of the contacts of the connector lead assemblyand the material may be allowed to cure in place. A sleeve may at leastsubstantially surround the coating. Typically, removal of the sleeve andthe coating from the connector lead assembly may be difficult toaccomplished without risk of damaging the connector lead assembly;especially in the case of electrical joints.

Some embodiments of the cap of the present technology include a chamberdefined in the cap body between the cap mating surface and the capnon-mating surface. FIG. 15 shows a radial cross section and alongitudinal cross section of a cap 1500 of the present technology. Thecap 1500 comprises a cap body 1510 generally defined by a cap non-matingsurface 1520 and a cap mating surface 1530. The cap body 1510 can bemade of silicone or polyurethane. The cap 1500 can include a drug-dopedcomponent as described in connection with cap 600.

The cap 1500 of FIG. 15 includes two chambers 1540, though caps inaccordance with the present technology can include one, or three or morechambers. Each chamber 1540 can extend longitudinally along some or amajority of the length of the cap. While each chamber 1540 shown in FIG.15 extends circumferentially through about 60 degrees, one or morechambers can extend around the full perimeter of the body 1510. Eachchamber 1540 can be bounded by a first chamber wall 1542 forming aportion of the non-mating surface 1520, and a second chamber wall 1543forming a portion of the mating surface 1530.

Both chamber walls 1542 and 1543 can have features that promote theelectrical insulating protection of an implantable medical deviceconnector lead assembly mated with the cap 1500. The second chamber wall1543 of FIG. 15 can more distendable in comparison to the first chamberwall 1542, such that upon a chamber filling with a filler (such asfiller 1660 of FIG. 16) the chamber will exert a sealing pressure on aportion of an implantable medical device connector lead assembly whenmated with the cap 1500. The first chamber 1542 wall can becomparatively less distendable by being of the same material as, butthicker than, the second chamber wall 1543. The first chamber wall 1542can be strengthened to resist distention by a reinforcement such asreinforcement 1550. The first chamber wall 1542 can be made from amaterial of greater durometer than the second wall 1543 to make it lessdistendable.

Referring to FIG. 16, cap 1500 is shown mating with a connector leadassembly 1690 of an implantable medical device. The connector leadassembly comprises a lead 1692 and a conductive pathway 1694 connectedto a contact 1696 disposed in a connector 1698. A filler 1680 can beintroduced into the chamber 1640, for example upon manufacturing of thecap 1500, or through port 1693 at surgery after the cap 1500 is placedover the connector lead assembly 1690. Pressure from the filler 1680 cancause the more distendable second chamber wall 1543 to distend, thuspromoting an electrically insulating seal around the portion of theconnector lead assembly 1690 mated to the cap 1500. In the case of FIG.16, contact 1696 is electrically sealed by at least partially filling atleast one chamber 1540.

Filler 1680 can be a biocompatible liquid selected from the groupconsisting of saline or liquid silicone which may be cured in situ. Asilicone can be a single-material filler, or a two-component filler,which when mixed, begins curing. A slit (not shown) may be created inthe port 1693 to facilitate access, e.g., through use of a blunt needle.It is not necessary to have a filling port, particularly of aself-curing filler is used.

While various embodiments of the present technology have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. For instance, while FIG. 1 illustratesa context of the present technology in which cochlear implant 100includes an external component 142, it would be appreciated that inalternative embodiments, cochlear implant 100 may be amostly-implantable or totally implantable medical device. For instance,embodiments of the cap technology described herein as interfacing withconnector lead assembly 510 can also be used as interfacing with aconnector directly on the body of the IMD. It will be apparent topersons skilled in the relevant art that various changes in form anddetail can be made therein without departing from the spirit and scopeof the technology. For instance, features described as part of oneimplementation can be used on another implementation to yield a stillfurther implementation. Thus, the breadth and scope of the presenttechnology should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and their equivalents.

1. A cap for protecting an electrical connector lead assembly of animplantable medical device, the cap comprising: a body having (1) amating surface configured to receive at least a portion of theelectrical conductor lead assembly of the implantable medical device andto electrically insulate a plurality of contacts of the electricalconductor lead assembly of the implantable medical device, and (2) anon-mating surface; and an electrical network disposed within the body.2. The cap of claim 1 further comprising: a removal feature, tofacilitate removal of the cap from the electrical connector leadassembly.
 3. The cap of claim 2, wherein: the removal feature comprisesat least one of a flap, a weakened region of the body, and a filamentembedded in the body. 4.-5. (canceled)
 6. The cap of claim 1, wherein:the mating surface defines an elongate volume for receiving the portionof the connector lead assembly.
 7. The cap of claim 1, wherein the capfurther comprises: a reinforcing element surrounding at least portion ofthe cap.
 8. The cap of claim 1, wherein the electrical network furthercomprises: first and second contacts exposed at the mating surface, afirst circuit element, and two conductive pathways connecting thecontacts to the circuit element; wherein the body is configured to matewith the electrical connector lead assembly such that each contactconductively engages a corresponding contact of the electrical connectorlead assembly when the cap and electrical connector lead assembly aremated.
 9. The cap of claim 8, wherein the first circuit elementcomprises: an electrical impedance.
 10. The cap of claim 8, wherein thefirst circuit element comprises: a magnetic induction coil.
 11. The capof claim 8, wherein the circuit element comprises at least one of: aconductive pathway, a resistor, a capacitor, and an inductor.
 12. Thecap of claim 8, wherein the cap further comprises: a second circuitelement series connected to the first circuit element; and a conductiveplate conductively exposed to an exterior of the cap and electricallyconnected to a conductive pathway between the series-connected circuitelements.
 13. The cap of claim 1, wherein the electrical networkcomprises an open circuit tester. 14.-25. (canceled)
 26. The cap ofclaim 1 wherein: the body has defined therein a chamber between themating surface and the non-mating surface; the chamber is bounded by: afirst chamber wall forming a portion of the non-mating surface, and asecond chamber wall forming a portion of the mating surface; and whereinthe second chamber wall is distendable in comparison to the firstchamber wall.
 27. The cap of claim 26 wherein the chamber extendscircumferentially around the body.
 28. The cap of claim 26 furthercomprising: a reinforcement in the body between the first chamber walland the non-mating surface.
 29. The cap of claim 26 further comprising:a filler in the chamber. 30.-31. (canceled)
 32. An apparatus comprising:a cap comprising: a cap body comprising an inner surface and an outersurface, wherein the inner surface is configured to receive andelectrically insulate at least one contact of an lead assembly; and anelectrical network disposed in the cap body, wherein when the leadassembly is received in the inner surface, the electrical network is incommunication with the at least one contact.
 33. The apparatus of claim32, wherein the electrical network comprises an open circuit tester. 34.The apparatus of claim 32, wherein the electrical network comprises: afirst circuit element and a second circuit element connected in seriesto the first circuit element; and a conductive plate conductivelyexposed on the outer surface and electrically connected to the firstcircuit element and the second circuit element.
 35. The apparatus ofclaim 32, wherein the inner surface comprises a distendable wall. 36.The apparatus of claim 35, wherein the inner surface is configured todistend when the lead assembly is received in the cap body.